1. Field of the Invention
This invention relates to the purification of alcohol selectively to remove internal hydroxyl groups such as those of the bivalent radial (&gt;CHOH) while leaving substantially unaffected the primary or terminal hydroxyl groups such as those of the monovalent radical (--CH.sub.2 OH).
2. Description of the Prior Art
The basic concept of purifying alcohol selectively to remove secondary hydroxyl groups is set forth by Wikman et al in U.S. Pat. No. 3,468,965. The purification is described as a selective dehydration of internal hydroxyl groups and preferably is followed by a mild hydrogenation to saturate unsaturated linkages, such as olefinic double bonds, resulting from or carried through the dehydration step. The process of U.S. Pat. No. 3,468,965 provides purification to meet the sulfate paste odor problem. The present invention seeks to provide an even further reduction of the content of molecules having internal hydroxyl groups. One of the catalysts described in U.S. Pat. No. 3,468,965 is a silicated alumina catalyst. As will be explained in greater detail hereinafter, the present invention uses an alumina catalyst which has been treated with a hydroxide of a Group 1-A metal, e.g. sodium hydroxide. The resulting catalyst provides an improved dehydration treatment wherein diols are eliminated to a high degree without producing excessive quantities of ethers. The present invention provides a process wherein the catalyst is easier to prepare than catalysts which require calcining such as the calcium oxide on alumina catalysts of U.S. Pat. No. 3,855,320.